This invention relates in general to surgical needles and, more particularly, to improvements in a biopsy needle construction which minimizes hemorrhagic complications upon removal of the needle from a site in a patient.
The invention is particularly applicable to the removal of tissue and like specimens from the human body and will be described in particular with reference thereto. It will be appreciated by those skilled in the art, however, that the invention has broader application and may be used for selective extraction of tissue samples and the like from other living matter such as animals.
A biopsy needle of the character to which the present invention relates is a side cut needle such as the type commercially known as "Trucut" needles. Such a side cut needle includes a solid stylet telescopically received within an inner tubular cannula which in turn is telescopically received within an outer tubular cannula by which the stylet and inner tubular cannula are supported for axial and rotative displacement relative to one another and to the outer cannula. The side cut needle is inserted into a patient until the distal end of the outer cannula reaches the lesion where the biopsy specimen is to be taken. The stylet is then advanced relative to the outer and inner cannulas into the lesion to the biopsy site. The stylet is provided with a cutting recess in the distal portion thereof and, when the stylet reaches the biopsy site, the stylet is rotated so that a cutting edge of the cutting recess severs the tissue. The inner cannula is then advanced relative to the outer cannula and over the stylet to cut the tissue into the cutting recess and to cover the recess and thus entrap the specimen within the recess for removal from the site by retracting the stylet and inner cannula into the outer cannula and then withdrawing the needle from the patient.
In a number of my prior U.S. Pat. Nos. 4,708,147; 4,838,280; 4,936,835; 5,080,655; and 5,195,988, and in my co-pending patent application Ser. No. 896,588 filed Jun. 10, 1992 entitled "Sheath For Wound Closure Caused By A Medical Tubular Device", the disclosure of all of which patents and co-pending application are incorporated herein by reference, there is disclosed a side cut needle of the foregoing character in which the equivalent of the inner cannula referred to above is provided with a tubular sheath of a absorbable gelatin material or a non-bioabsorbable hemostatic collagen for minimizing bleeding of the patient from the biopsy site upon removal of the needle. In this respect, the hemostatic sheath is applied about the distal portion of the inner cannula and is advanced therewith into the lesion for the inner cannula to cover the cutting recess in the stylet which, as described above, is initially inserted into the lesion and rotated to sever a biopsy specimen to be removed from the lesion. In accordance with my earlier arrangements, the equivalent of the outer cannula referred to hereinabove is also inserted into the lesion and has a distal end adjacent the axially inner end of the hemostatic sheath for positioning the sheath in the location where the biopsy specimen was taken when the specimen is withdrawn therefrom. More particularly in this respect, when the biopsy specimen is cut and enclosed in the cutting recess as described above, the stylet and inner cannula are withdrawn or retracted relative to the outer cannula which is held stationary at the site, whereby the axially inner end of the sheath engages the outer cannula and is held in its position within the lesion as the inner cannula and stylet are retracted into the outer cannula. When the sheath is released from the inner cannula, the needle is withdrawn from the site of the lesion.
While the hemostatic sheath in my earlier arrangements serves its intended purpose to minimize bleeding from the biopsy site by compressing the bleeding tissue surrounding the biopsy site and by swelling upon absorbing body fluid so as to increase the compressive effect, there are a number of disadvantages with respect to the structure and manipulation of the component parts of the biopsy needle in connection with obtaining a biopsy specimen. More particularly in this respect, by providing the hemostatic sheath in the form of a sleeve surrounding the inner cannula and which sleeve has an outer diameter generally corresponding to that of the outer cannula in a standard side cut biopsy needle, the diameter of the needle portion which must penetrate the lesion is greater than that required with a standard side cut needle wherein only the stylet and inner cannula need penetrate the lesion in order to obtain a biopsy specimen therefrom. Thus, the size of the puncture as the needle penetrates the lesion is larger than with a standard side cut needle, whereby the possibility of severing blood vessels while positioning the needle and severing the biopsy specimen is increased as is the resultant bleeding caused thereby.
In addition to the above, the standard side cut needle has to be modified to include an outer cannula which axially accommodates the hemostatic sleeve on the outer periphery of the inner cannula and which operates to push the sleeve off of the latter at the biopsy site following severing and covering of the biopsy specimen. Accordingly, automated operation of the needle through the use of a conventional "gun" which will actuate the standard Trucut needle to advance and rotate the stylet, advance the inner cannula to cover the specimen cutting recess in the stylet, and retract the stylet and inner cannula relative to the outer cannula is not possible. Therefore, the component parts of the needle must be manually manipulated to retrieve a biopsy specimen. Moreover, the manual manipulation of the component parts of the needle is much more complex than that required to manually retrieve a biopsy specimen using a standard side cut needle. In this respect, after the stylet has been extended into the biopsy site and rotated to severe the specimen, both the inner cannula with the hemostatic sheath thereon and the outer cannula axially behind the sheath must be advanced into the biopsy site so as to cover the specimen cutting recess in the stylet and position the outer cannula to engage and hold the hemostatic sheath at the biopsy site during retraction of the inner cannula and stylet therefrom. Still further, the latter requires holding the outer cannula in place and simultaneously withdrawing the inner cannula and stylet thereinto so as to displace the hemostatic sheath from the inner cannula. Such manual manipulations of the component parts of the needle are more time consuming than desirable and increase the possibility of movements being imparted to the needle during such manipulation which in turn increase the possibility of hemorrhagic complications.
Yet a further disadvantage of my earlier biopsy needle resides in the fact that the hemostatic sheath in being disposed about the inner cannula and forwardly of the distal end of the outer cannula is exposed to infectious micro-organisms prior to use and to body fluids from the time of initial penetration of the patient's body until such time as the sheath is positioned at the biopsy site and displaced from the inner cannula. If the material of the sheath is a gelatin material or a hemostatic collagen, the material of the sheath begins to absorb body fluids immediately upon exposure thereto and to swell. It will be appreciated, therefore, that by the time the stylet has been advanced into the lesion and rotated to sever the biopsy specimen, the outer diameter of the sleeve may have increased considerably whereby advancement of the inner cannula into the biopsy site with the hemostatic sheath thereabout enlarges the puncture an thus the possibility of rupturing blood vessels even beyond that resulting from the larger initial diameter of the hemostatic sheath relative to that of the inner cannula in a standard needle construction.